Solvent extraction behavior of rare earth ions with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone

Solvent extraction behaviour of all rare earth ions (excepting promethium) and yttrium have been investigated using 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (HPMBP) as the extractant in aqueous-chloroform medium at 25 +- 10C. The initial concentration of HPMBP was 5 x 10-2M, and the aqueous phase was maintained at constant ionic strength 0.1 M(Na, H)+C104-. From distribution coefficients (D), extraction equilibrium constants (K*sub(3,0)), for the formation of Ln (PMBP)3, two-phas e stability constants (logβ3.Psub(Ln(PMBP)3)), pH for 50% extraction of metal chelates (pH50) and separation factors (S) between the adjacent elements have been evaluated. These values have been examined in the light of double-double effect and tetrad effect. A plot of log K*sub(3,0) values against atomic number Z show tetrad grouping. A similar plot of log K*sub(3,0) values against L (total angular momentum of rare earth ions) forms an 'inclined W', agreeing with a recent suggestion of Sinha. On the other hand, logβ3.Psub(Ln(PMBP)3) values versus r-1 (r, ionic radii of rare earth ions) may be fitted into two straight lines for the lower and higher members of the series with a break at gadolinium. (author)